UPSC Prelims 2025 Q22: Andes Mountains and Countries — Explained
Consider the following countries:
I. Bolivia
II. Brazil
III. Colombia
IV. Ecuador
V. Paraguay
VI. Venezuela
Andes mountains pass through how many of the above countries?
- Only two
- Only three
- Only four
- Only five
Answer: (c) Only four
Statement-wise explanation
- I: correct — The Andes cross western Bolivia as two parallel ranges, the Cordillera Occidental and the Cordillera Oriental (Real). Between them lies the Altiplano, a high plateau that holds Lake Titicaca on the Peru border. Bolivia is landlocked, but its western part is Andean.
- II: incorrect — The Andes stop before they reach Brazil. Brazil's land is mostly the Amazon basin, the Brazilian Highlands and the Guiana Highlands. Even Brazil's far western Amazon border with Peru and Bolivia is lowland at the eastern foot of the Andes.
- III: correct — In Colombia the Andes split into three ranges: the Cordillera Occidental, Central and Oriental. The Magdalena and Cauca river valleys run between them. Bogotá stands on the Eastern Cordillera.
- IV: correct — Ecuador is crossed by two parallel Andean ranges. One faces the Pacific and the other slopes down toward the Amazon basin. Volcanoes such as Chimborazo and Cotopaxi rise along these ranges, with Quito in the high valley between them.
- V: incorrect — Paraguay is a landlocked lowland country that lies east of the Andes. The Paraguay River splits it into the Gran Chaco plain in the west and hilly lowland in the east. The Andes reach Bolivia and Argentina but stop before Paraguay.
- VI: correct — The northernmost Andes are in Venezuela. They run as the Cordillera de Mérida, parallel to the Caribbean coast, before turning southwest into Colombia. So the Andes pass through Bolivia, Colombia, Ecuador and Venezuela: four of the six countries listed.
How to eliminate
To solve this you need to know which countries the Andes cross. The fact to remember is the seven Andean countries, north to south: Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile, Argentina. Two map checks also help. First, the Andes run along the Pacific (western) side of South America, so any country with no western highland is out. Brazil and Paraguay both lie east of the range, in the Amazon basin, the Brazilian Highlands and the Chaco–Paraná lowlands. Second, Venezuela is the classic trap: many aspirants forget that the Andes curve east along the Caribbean coast into Venezuela as the Cordillera de Mérida. Bolivia is a second trap, because 'landlocked' does not mean 'not Andean'. Remove Brazil and Paraguay and four countries remain. Note that Peru, Chile and Argentina were left out of the list on purpose, so the question turns on the border cases.
Know more
The Andes are the world's longest continental mountain range, about 8,900 km long. They run north to south along the western edge of South America. They are young fold mountains with many volcanoes. They were raised where the oceanic Nazca Plate sinks (subducts) under the South American Plate. That is an ocean–continent convergent boundary, the same type that produces the Peru–Chile Trench offshore.
| Country (north → south) | Andean feature to remember |
|---|---|
| Venezuela | Cordillera de Mérida, parallel to the Caribbean coast |
| Colombia | Three cordilleras: Occidental, Central, Oriental |
| Ecuador | Two parallel ranges with volcanoes (Chimborazo, Cotopaxi) |
| Peru | Cordillera Blanca; Lake Titicaca on the Bolivia border |
| Bolivia | Altiplano plateau between two cordilleras |
| Chile | Atacama Desert lies west of the range; copper belt |
| Argentina | Aconcagua (6,959 m), the highest peak outside Asia, near the Chile border |
Non-Andean South American countries: Brazil, Paraguay, Uruguay, Guyana, Suriname and French Guiana (an overseas region of France). Their relief comes from older shields and plains: the Guiana Highlands, the Brazilian Highlands, the Amazon basin, the Gran Chaco and the Pampas fringe.
Related facts UPSC likes:
- The Andes act as a rain barrier. Together with the cold Humboldt (Peru) Current, they help keep the Atacama Desert one of the driest places on Earth.
- The Lithium Triangle (Bolivia, Argentina, Chile) lies in the salt flats of the high Andes.
- The Uspallata Pass links Mendoza (Argentina) with Santiago (Chile).
- Compare the Rockies in North America, which are also young fold mountains on the Pacific side of the Americas.
NCERT Concepts to Revise
- Andes: The question tests how far this range runs along South America's western edge and which listed countries it reaches.
- Fold mountain: The Andes are young fold mountains, which explains their long, narrow north–south belt along the continent's edge.
- Subduction zone: The Nazca Plate sinking under South America built the Andes, so the range follows the Pacific margin.
- Convergent boundary: The Andes sit on an ocean–continent convergent boundary, which shows why the range hugs the west coast.